// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
/*
 ******************************************************************************
 * Copyright (C) 1996-2011, International Business Machines Corporation and   *
 * others. All Rights Reserved.                                               *
 ******************************************************************************
 */

package com.ibm.icu.lang;

import com.ibm.icu.impl.UCharacterName;
import com.ibm.icu.impl.UCharacterNameChoice;
import com.ibm.icu.util.ValueIterator;

/**
 * Class enabling iteration of the codepoints and their names.
 *
 * <p>Result of each iteration contains a valid codepoint that has valid name.
 *
 * <p>See UCharacter.getNameIterator() for an example of use.
 *
 * @author synwee
 * @since release 2.1, March 5 2002
 */
class UCharacterNameIterator implements ValueIterator {
    // public methods ----------------------------------------------------

    /**
     * Gets the next result for this iteration and returns true if we are not at the end of the
     * iteration, false otherwise.
     *
     * <p>If the return boolean is a false, the contents of elements will not be updated.
     *
     * @param element for storing the result codepoint and name
     * @return true if we are not at the end of the iteration, false otherwise.
     * @see com.ibm.icu.util.ValueIterator.Element
     */
    @Override
    public boolean next(ValueIterator.Element element) {
        if (m_current_ >= m_limit_) {
            return false;
        }

        if (m_choice_ == UCharacterNameChoice.UNICODE_CHAR_NAME
                || m_choice_ == UCharacterNameChoice.EXTENDED_CHAR_NAME) {
            int length = m_name_.getAlgorithmLength();
            if (m_algorithmIndex_ < length) {
                while (m_algorithmIndex_ < length) {
                    // find the algorithm range that could contain m_current_
                    if (m_algorithmIndex_ < 0
                            || m_name_.getAlgorithmEnd(m_algorithmIndex_) < m_current_) {
                        m_algorithmIndex_++;
                    } else {
                        break;
                    }
                }

                if (m_algorithmIndex_ < length) {
                    // interleave the data-driven ones with the algorithmic ones
                    // iterate over all algorithmic ranges; assume that they are
                    // in ascending order
                    int start = m_name_.getAlgorithmStart(m_algorithmIndex_);
                    if (m_current_ < start) {
                        // this should get rid of those codepoints that are not
                        // in the algorithmic range
                        int end = start;
                        if (m_limit_ <= start) {
                            end = m_limit_;
                        }
                        if (!iterateGroup(element, end)) {
                            m_current_++;
                            return true;
                        }
                    }
                    /*
                    // "if (m_current_ >= m_limit_)" would not return true
                    // because it can never be reached due to:
                    // 1) It has already been checked earlier
                    // 2) When m_current_ is updated earlier, it returns true
                    // 3) No updates on m_limit_*/
                    if (m_current_ >= m_limit_) {
                        // after iterateGroup fails, current codepoint may be
                        // greater than limit
                        return false;
                    }

                    element.integer = m_current_;
                    element.value = m_name_.getAlgorithmName(m_algorithmIndex_, m_current_);
                    // reset the group index if we are in the algorithmic names
                    m_groupIndex_ = -1;
                    m_current_++;
                    return true;
                }
            }
        }
        // enumerate the character names after the last algorithmic range
        if (!iterateGroup(element, m_limit_)) {
            m_current_++;
            return true;
        } else if (m_choice_ == UCharacterNameChoice.EXTENDED_CHAR_NAME) {
            if (!iterateExtended(element, m_limit_)) {
                m_current_++;
                return true;
            }
        }

        return false;
    }

    /**
     * Resets the iterator to start iterating from the integer index UCharacter.MIN_VALUE or X if a
     * setRange(X, Y) has been called previously.
     */
    @Override
    public void reset() {
        m_current_ = m_start_;
        m_groupIndex_ = -1;
        m_algorithmIndex_ = -1;
    }

    /**
     * Restricts the range of integers to iterate and resets the iteration to begin at the index
     * argument start.
     *
     * <p>If setRange(start, end) is not performed before next(element) is called, the iteration
     * will start from the integer index UCharacter.MIN_VALUE and end at UCharacter.MAX_VALUE.
     *
     * <p>If this range is set outside the range of UCharacter.MIN_VALUE and UCharacter.MAX_VALUE,
     * next(element) will always return false.
     *
     * @param start first integer in range to iterate
     * @param limit 1 integer after the last integer in range
     * @exception IllegalArgumentException thrown when attempting to set an illegal range. E.g limit
     *     <= start
     */
    @Override
    public void setRange(int start, int limit) {
        if (start >= limit) {
            throw new IllegalArgumentException(
                    "start or limit has to be valid Unicode codepoints and start < limit");
        }
        if (start < UCharacter.MIN_VALUE) {
            m_start_ = UCharacter.MIN_VALUE;
        } else {
            m_start_ = start;
        }

        if (limit > UCharacter.MAX_VALUE + 1) {
            m_limit_ = UCharacter.MAX_VALUE + 1;
        } else {
            m_limit_ = limit;
        }
        m_current_ = m_start_;
    }

    // protected constructor ---------------------------------------------

    /**
     * Constructor
     *
     * @param name name data
     * @param choice name choice from the class com.ibm.icu.lang.UCharacterNameChoice
     */
    protected UCharacterNameIterator(UCharacterName name, int choice) {
        if (name == null) {
            throw new IllegalArgumentException(
                    "UCharacterName name argument cannot be null. Missing unames.icu?");
        }
        m_name_ = name;
        // no explicit choice in UCharacter so no checks on choice
        m_choice_ = choice;
        m_start_ = UCharacter.MIN_VALUE;
        m_limit_ = UCharacter.MAX_VALUE + 1;
        m_current_ = m_start_;
    }

    // private data members ---------------------------------------------

    /** Name data */
    private UCharacterName m_name_;

    /** Name choice */
    private int m_choice_;

    /** Start iteration range */
    private int m_start_;

    /** End + 1 iteration range */
    private int m_limit_;

    /** Current codepoint */
    private int m_current_;

    /** Group index */
    private int m_groupIndex_ = -1;

    /** Algorithm index */
    private int m_algorithmIndex_ = -1;

    /** Group use */
    private static char GROUP_OFFSETS_[] = new char[UCharacterName.LINES_PER_GROUP_ + 1];

    private static char GROUP_LENGTHS_[] = new char[UCharacterName.LINES_PER_GROUP_ + 1];

    // private methods --------------------------------------------------

    /**
     * Group name iteration, iterate all the names in the current 32-group and returns the first
     * codepoint that has a valid name.
     *
     * @param result stores the result codepoint and name
     * @param limit last codepoint + 1 in range to search
     * @return false if a codepoint with a name is found in group and we can bail from further
     *     iteration, true to continue on with the iteration
     */
    private boolean iterateSingleGroup(ValueIterator.Element result, int limit) {
        synchronized (GROUP_OFFSETS_) {
            synchronized (GROUP_LENGTHS_) {
                int index = m_name_.getGroupLengths(m_groupIndex_, GROUP_OFFSETS_, GROUP_LENGTHS_);
                while (m_current_ < limit) {
                    int offset = UCharacterName.getGroupOffset(m_current_);
                    String name =
                            m_name_.getGroupName(
                                    index + GROUP_OFFSETS_[offset],
                                    GROUP_LENGTHS_[offset],
                                    m_choice_);
                    if ((name == null || name.length() == 0)
                            && m_choice_ == UCharacterNameChoice.EXTENDED_CHAR_NAME) {
                        name = m_name_.getExtendedName(m_current_);
                    }
                    if (name != null && name.length() > 0) {
                        result.integer = m_current_;
                        result.value = name;
                        return false;
                    }
                    ++m_current_;
                }
            }
        }
        return true;
    }

    /**
     * Group name iteration, iterate all the names in the current 32-group and returns the first
     * codepoint that has a valid name.
     *
     * @param result stores the result codepoint and name
     * @param limit last codepoint + 1 in range to search
     * @return false if a codepoint with a name is found in group and we can bail from further
     *     iteration, true to continue on with the iteration
     */
    private boolean iterateGroup(ValueIterator.Element result, int limit) {
        if (m_groupIndex_ < 0) {
            m_groupIndex_ = m_name_.getGroup(m_current_);
        }

        while (m_groupIndex_ < m_name_.m_groupcount_ && m_current_ < limit) {
            // iterate till the last group or the last codepoint
            int startMSB = UCharacterName.getCodepointMSB(m_current_);
            int gMSB = m_name_.getGroupMSB(m_groupIndex_); // can be -1
            if (startMSB == gMSB) {
                if (startMSB == UCharacterName.getCodepointMSB(limit - 1)) {
                    // if start and limit - 1 are in the same group, then enumerate
                    // only in that one
                    return iterateSingleGroup(result, limit);
                }
                // enumerate characters in the partial start group
                // if (m_name_.getGroupOffset(m_current_) != 0) {
                if (!iterateSingleGroup(result, UCharacterName.getGroupLimit(gMSB))) {
                    return false;
                }
                ++m_groupIndex_; // continue with the next group
            } else if (startMSB > gMSB) {
                // make sure that we start enumerating with the first group
                // after start
                m_groupIndex_++;
            } else {
                int gMIN = UCharacterName.getGroupMin(gMSB);
                if (gMIN > limit) {
                    gMIN = limit;
                }
                if (m_choice_ == UCharacterNameChoice.EXTENDED_CHAR_NAME) {
                    if (!iterateExtended(result, gMIN)) {
                        return false;
                    }
                }
                m_current_ = gMIN;
            }
        }

        return true;
    }

    /**
     * Iterate extended names.
     *
     * @param result stores the result codepoint and name
     * @param limit last codepoint + 1 in range to search
     * @return false if a codepoint with a name is found and we can bail from further iteration,
     *     true to continue on with the iteration (this will always be false for valid codepoints)
     */
    private boolean iterateExtended(ValueIterator.Element result, int limit) {
        while (m_current_ < limit) {
            String name = m_name_.getExtendedOr10Name(m_current_);
            if (name != null && name.length() > 0) {
                result.integer = m_current_;
                result.value = name;
                return false;
            }
            ++m_current_;
        }
        return true;
    }
}
